Update documentation to include i3 instructions

docs/source/overview.rst

@@ -73,6 +73,7 @@ Python packages
 * ``pygit2``
 * ``mercurial``
 * ``psutil``
+* ``i3-py``, `available on github <https://github.com/ziberna/i3-py>`_. Only used with i3wm bindings and segments.
 
 Other applications
 ^^^^^^^^^^^^^^^^^^
@@ -233,3 +234,19 @@ Add the following to your :file:`~/.config/qtile/config.py`:
            ),
        ),
    ]
+
+with i3bar replacement
+-----------------
+
+.. note:: Until the patch is done in i3, you will need a custom ``i3bar`` build called ``i3bgbar``.
+    The source is available `here <https://github.com/S0lll0s/i3bgbar>`_.
+
+Add the following to your :file:`~/.i3/config`::
+    bar {
+        i3bar_command i3bgbar
+
+        status_command python /path/to/powerline/bindings/i3/powerline-i3.py
+        font pango:PowerlineFont 12
+    }
+
+where ``i3bgbar`` may be replaced with the path to the custom i3bar binary and ``PowerlineFont`` is any system font with powerline support.